The British Miniature Horse (also known as 'British Toyhorse') is a miniature breed, that was created by crossing small Shetlands with small British ponies of various breeds.

The conformation of British Miniature Horses can vary greatly between one horse to another. For example, some horses have a lean conformation characterized by a dished head, a long and arched neck, a thin girth, and thin legs, while other horses have a more "pony-like" conformation characterized by a coarser head, a shorter and thicker neck, a deeper girth, a wider body, and thicker legs. British Miniature Horses in Horse Isle have the latter conformation, because the leaner one is more characteristic to American Miniature Horses rather than to British Miniature Horses.

When it comes to breeding rules, the British Miniature Horse Society accepts for full registration only horses who were born to two British Miniature parents. Therefore, in Horse Isle, the British Miniature Horse has a closed studbook, meaning that crossing a British Miniature Horse with a horse of a different breed will result in a non-pure foal.

British Miniature Horses come in all colors and patterns except for dominant black and manchado, though these two can be bred into them. The maximal height allowed is 8.2hh, and there's no minimum height limit. In Horse Isle, they stand between 6.2hh and 8.2hh.